Process for electrodepositing an adherent coating of copper on chromium-contanining alloys of iron and/or nickel



Patented June 9, 1942 PROCESS FOR ELECTRODEPOSITING AN ADHERENT COATING OF COPPER ON CHROMIUM CONTAINING ALLOYS OF IRON AND/OR NICKEL Andrew Wesley, Plainfield, N. J assignor to The International Nickel Company, Inc., New York, p N. Y.', a corporation of Delaware No Drawing. Application December 1, 1937,

Serial No. 177,462

4 Claims.

'rne present invention relates toa process for obtaining an adherent coating of electrode-,

posited material on.a chromium-containing alloy of iron and/or nickel, and, more particularly, to

a process for obtaining an adherent coating of electrodeposited copper on nickel-chromium-iron alloys of the stainless type.

For certain purposes, it is desirable to have a composite metal, one layer of which is copper and another layer of which contains chromium or is constituted of a nickel-chromium-iron alloy. Considerable difficulty has heretofore been experienced in securing good adherence between the surface of a chromium-containing article, especially a nickel-chromium alloy of the stainless type and the surface of copper when the latter was formed by electrodeposition. Without satisfactory adherence between the foundation metal and the electrodeposited layer it is not possible to work or fabricate the product,

particularly to cold roll, draw or work the product without great losses due to the tendency of the layers to pull apart in spots or to separate altogether.

The problem of electrodepositing an adherent layer of copper or nickel-chromium'products of the stainless type has inspired considerable research, but none of the processes developed, as far'as I am aware, has been entirely convenient,

thoroughly reliable, and wholly satisfactory and I have discovered a process for obtaining an adherent coating of electrodeposited metal on a body made of chromium-containing alloy, such as a nickel-chromium alloy, stainless steel or the like, which involves the step of protecting the body after removal of the passive film with a film of metal which effectively prevents the formation of a detrimental passive film during the transfer of the body from the preparatory bath to the regular plating bath and which can be carried into commercial practice on an inclustrial scale conveniently, readily and safely even with large size articles or products.

It is an object of the present invention to provide a process for obtaining an adherent coating of electrodeposited metal on a body made of chromium-containing alloy, such as a nickelchromium alloy, stainless steel, or the like.

It is another object of the invention to provide a' process for protecting a body made of a chromium-containing alloy from which the passive film has been removed in a preparatory bath Thus, certain processes attempted acid solution to an electroplating bath while still mium alloys from one tank to another in commercial practice rapidly enough to avoid danger of partial formation of a passive film on the article during the transfer period.

-60 to transfer large articles made of nickel-chm and on which a protective metallic film is applied to prevent the reforming of such a passive film while the body is being transferred to a regular bath for plating a metallic layer such as copper.

A further object of the invention is the provision of a process for protecting a body made of chromium-containingalloy from which the passive film has been removed in a preparatory bath containing hydrochloric acid against reforming of such a film while the body is being transferred to a regular metal plating bath by forming on said body a protective metallic film while it is immersed in the preparatory bath.

It is within the contemplation of the invention to provide a process for electrodepositing a thick coating of copper on a body made of a nickel-chromium alloy, stainless steel or the like,

chromium alloy, stainless steel or the like which can be practiced on an industrial scale with conventional appliances and equipment and which is relatively cheap and permits wide commercial and industrial use.

Other objects and advantages of the invention it with a film of protective metal without remov- A ing the body from the situs of the first operation, and forming upon the body an adherent layer of electrodeposited metal.

The article or body to be coated, which is made of a chromium-containing alloy, is preferably freed from grease in the customary manner and then immersed in a bath containing hydrochloric acid to remove a passive film that forms on the surface of a chromium-containing alloy when it is exposed to air. To prevent the passive film from reforming upon removal into the air from the acid solution, the article or body is not removed from the acid bath after the destruction of the passive film, but is coated, while still in the acid solution, with a layer, film or plate of a protective metal, such as nickel. that I can accomplish the production of the formation of the nickel plate by adding an appropriate amount of nickel chloride to the solution containing hydrochloric acid and electrodepositing a film or plate of nickel upon the chromium-bearing surface of the article or body whil it is still immersed in the hydrochloric acid solution. Thereafter the article or body protected by a nickel plate or film can be safely removed from my special preparatory bath and transferred to the regular copper plating bath or the like without danger of the reforming or healing of the passive film. The coating metal, such as copper, is then electrodeposited upon the article or body in the usual manner. It. has been found that the copper adheres tenaciously to the nickel-plated article or body and can be worked and fabricated without rupturing the bond between the layers.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative example is given.

A body or article made of a nickel-chromiumiron alloy containing about 79% nickel, about 13% chromium, and about 7% iron was pumice scrubbed until there was no water break. The surface of the body or article may, of course, be degreased by any other suitable method,

. The body or article of nickel-chromium-iron alloy was then immersed in an acid nickel chloride solution having the following composition:

Grams per liter NiC12.6H2O about 240 HCl about 36 The temperature of the solution was kept at about 70 F. It will be evident that the removal of the passive film could be accomplished in a solution containing no nickel chloride and that this salt could be added thereto in proper amount after the passive film had been removed. I

The nickel-chromium article or body was made anode for about 2 minutes at a current density of about amperes per square foot (2.2 amperes per square decimeter) using nickel electrodes as cathodes. While the article was maintained in the solution, the electric current was then re- I have found.

anodically treated surface of the article for about 6 minutes at a current density of about 20 amperes per square foot (2.2 amperes per square decimeter).

The article now protected by nickel plate was removed from the solution and transferred without rinsing to an acid copper sulphate plating solution of the usual composition. For instance, the following composition gave satisfactory results:

Grams per liter CUSO4.5H2O about 200 H2504 about 100 By using a current density of aout 50 amperes per sq. ft. (5.4 amp. per sq. dm.) and a temperature of about 20 C. with good agitation, a plate, layer or coating of copper was deposited upon it.

The composite body formed was characterized by such tenacious adherence of the copper layer to the foundation of the article that the bond was not broken when the,body was worked or fabricated including such working or fabricating operations as cold rolling or drawing. Satisfactory results were obtained by using a nickelchromium article having a thickness of about 0.03 of an inch (0.08 centimeter), a nickel protective film of about 0.00004 of an inch (0.0001 centimeter), and a copper layer of about 0.08 of an inch (0.2 centimeter).

I claim:

1. A process for producing copper plated chromium-containing bodies capable of withstanding accentuated cold rolling, drawing or working without separation of the copper plating therefrom which comprises degreasing a body containing about 79% nickel, about 7% iron and about 13% chromium, immersing said body in a preparatory solution containing about 240 grams per liter of nickel chloride and about 36 grams per liter of hydrochloric acid, making said body the anode of an electric circuit having nickel versed and nickel was electrodeposited on the 76 electrodes as cathodes, passing a current of about 20 amperes per square foot through said solution for about 2 minutes at a temperature of about 70 F., making said body the cathode and said nickel electrodes the anodes in said circuit, passing a current through said circuit at a current density of about 20 amperes per'square foot until a protective layer of nickel has been deposited on said body, only then removing said nickel plated body from said preparatory solution and transferring said nickel plated body to a copper plating bath containing about 200 grams of copper sulfate and about grams of sulfuric acid per liter, and electroplating thereon a layer of copper at a current density of about 50 amperes per square foot whereby a composite chromium containing body having a copper plating and capable of withstanding severe cold working without separation of the copper layer from the aforesaid body is produced.

2. A process for producing chromium-containing bodies having a thick plate of copper and capable of withstanding accentuated working including rolling and drawing without separation of the thick copper plating therefrom, which comprises immersing a degreased body containing about 79% nickel, about 13% chromium and about 7% iron as an anode in an aqueous preparatory solution containing about 36 grams of hydrochloric acid per liter, passing a current of about 20 amperes per square foot for about 2 minutes through said preparatory solution to remove anodically a passive surface film from accuse said body and to provide said body with an active surface, making said body the cathode of an electric circuit having nickel anodes and having said aqueous preparatory solution as an elec-- passing an electric current at a current density ,of at least about 20 amperes per square foot through said solution containing nickel chloride until a thin protective layer of nickel having a thinness of about 0.0004 inch is electrodeposited on the active surface of said body, then transferring said nickel plated body to an aqueous copper plating bath containing essentially about 200 grams of copper sulfate and about 100 grams of sulfuric acid per liter, and electroplating on said thinly nickel plated chromium-containing body a thicker layer of copper at a current density of about 50 amperes per square foot whereby a thickly copper plated composite chromiumcontaining body capable of withstanding accentuated cold rolling without separation of the thick copper plating from the aforesaid chromiurn-containing body is produced.

3. A process for producing chromium-containing bodies having a thick copper plating and capable of withstanding accentuated working including rolling and drawing without separation of the thick copper plating therefrom, which comprises immersing a body made from an alloy containing chromium and at least one metal selected from the group consisting of nickel and iron in an aqueous preparatory solution con- 7 taining about 36 grams per liter of hydrochloric acid and nickel chloride, anodicaliy removing a passive surface film from the surface of said body by a current of about 20 amperes per square tectively plated chromium-containing body having a thin protective layer of said nickel. and thereafter transferring the protectively plated body to an aqueous acid copper plating bath and electrodepositing athicker layer of copper on said thin layer of nickel of said protectively plated body whereby a composite chromium-con.-

taining body having a thick plate of copper and capable of withstanding accentuated cold working without separation of the thick copper plating from the aforesaid body is produced.

4. A process for'producing chromium containing bodies having a thick plate of copper and capable of withstanding accentuated working in- 7 eluding rolling. and drawing without separation of the thick copper plating from the base metal which comprises producing in an aqueous bath containing 36 grams of hydrochloric acid per liter an active surface on a degreased chromiumcontaining body by anodically treating at a current density of about 20 amperes per square foot for a period of time of at least 2 minutes in .said aqueous ba'th, adding about '240grams per liter of nickel chloride to said bath containing 36 grams of hydrochloric acid per liter, making said body having an active surface the cathode 0.00004 inch on said active surface. then transfoot for 2 minutes to leave an active surface.

eiectrodepositing a thinprotective layer of nickel on the active surface of said body from said aqueous preparatory solution to produce a proferring said thinly nickel plated chromium-containing body to an aqueous acid copper sulfate bath, and electrodepositing a thicker copper layer on said thin nickel surface whereby a composite chromium-containing body having a thick plate of copper and capable of withstanding accentuated cold working including deep drawing without separation of the copper from the aforesaid chromium-containing body is produced.

ANDREWWESLEY. 

